When solving material balances for this distillation process, use the dropdown menu to start with a unit that has zero degrees of freedom or start with the complete system if it has zero degrees of freedom. Then, do a degree-of-freedom analysis on another unit to see if it now has zero degrees of freedom. Repeat this procedure until all of the unknown variables are determined.

In this simulation, a degree-of-freedom analysis is performed on a distillation process to determine whether the system has sufficient information to solve for the unknown variables. Use buttons to select the unit on which to do mass balances (distillation column, condenser, or reboiler) or to do a balance on the overall system. When “condenser” is selected, use buttons to select “partial condenser” or “total condenser”. Set the “total number of unknowns” with the slider; unknown variables are colored blue on the diagram and known variables are black. The known variables are selected randomly, and they change when you click the “new problem” button. Use buttons to select how species B is represented: as z_B or as 1 – z_A; the degree-of-freedom analysis is different for each representation. An explanation of the analysis is shown on the right. For zero degrees of freedom, the balances are solvable. The system is overspecified if it has more equations than unknowns and it is underspecified if it has more unknowns than equations. For a reboiler, the equilibrium ratio K_r, is known, and for a partial condenser the equilibrium ratio K_c is known. Temperatures and pressures are known for this analysis. Mass balances and phase equilibrium relations are solved to determine the unknown variables.

This simulation was created in the Department of Chemical and Biological Engineering, at University of Colorado Boulder for LearnChemE.com by Rachael Baumann under the direction of Professor John L. Falconer and was converted to HTML5 by Vlad Denisenkov. This simulation was prepared with financial support from the National Science Foundation. Address any questions or comments to learncheme@gmail.com. All of our simulations are open source, and are available on our LearnChemE Github repository.

If this simulation is too big for your screen, zoom out using  +  on Mac or  +  on Windows. To zoom in, use  +  on Mac or  +  on Windows.